Geography 1010

Remote Sensing

Contact Information

• Dr. Craig Coburn– Office: University Hall C-854– Phone: 317-2818– e-mail: craig.coburn@uleth.ca– Office Hours: 11-12:00 Tuesday, Thursday.

• Research Interests:– Remote Sensing Instrumentation.– Digital Image Processing.– Bidirectional Reflectance.– Environmental Applications of Remote Sensing Technology.– Data Sonification.

Today’s Lecture

• What is Remote Sensing?

• Remote Sensing in a Geographic Context.

• Electromagnetic Radiation.

• Spectral Signatures.

What is Remote Sensing?

• Sensing without contact.

• Gathering data from a distance.

• Fundamental to all sentient life forms.

• Two principle senses – sight and sound.

• Sight and sound have similar physiological and psychological underpinnings.

Physiology of Remote Sensing

• Physiology.– Data gathering instruments (Eyes – Ears).– Instruments are sensitive to different frequencies.

• Sound is a longitudinal mechanical wave of any frequency.

• Travels at a speed of 340 msec-1 at room temperature at sea level.

• The human ear has receptors that can detect sound frequencies raging from 20 vibrations to 20,000 vibrations per second.

Physiology of Remote Sensing

• Sight is similar to sound.• Electromagnetic Energy.• 299,792,458 msec-1 (vs.

340 msec-1 for sound).• Involves sensing light at

different frequencies.• The visible spectrum is

limited in frequency to between 400 and 700 nm.

Psychology of Remote Sensing

• Sensor take input and pass them along to the brain.

• The brain makes the interpretations and connections.

• Stereoscopic vision and hearing…all a function of the brain.

• Colour production for sight happens in the brain.

• Eye’s collect data – Brain produces information.

Remote Sensing in a Geographic Context.

• Maps have a long human tradition as a method of conveying geographic knowledge.– Abstract, symbolic, universal language.

• Until recently we did not have complete mapped coverage of the Earth.– Mostly resolved in the 1600’s.– Not “complete” until the early 1800’s.– That’s only about 6 generations of human existence

with knowledge about the globe.

Remote Sensing in a Geographic Context.

• Map making was a laborious task.

• Information from voyages of exploration (exploitation?).

• Hand-drafted maps were very expensive and had to be created by being there.– Ground Surveys.– Sailing.

Remote Sensing Development

• Someone invented the photographic process (disputed time – inventor).

• Invention of photographic process allowed for image collection for the first time.

• Able to collect “Bird’s Eye View” of many areas.

• Development pace increases exponentially in this field.

Aerial Photography.

• First truly useful form of remote sensing in Geography.

• Photographs from balloons and kites were not captured for purely Geographic purposes.

Aerial Photography Boston – 1860.

Aerial Photography

• WW1 was the first time aerial photography was extensively used for recording geography…human geography.

• Knowledge of enemy location is important.

Aerial Photography

• Airplanes are much more stable than balloons or kites.

• Better chance of developing a clear picture.– Planes at this point are not all that fast.

• Other platforms were also tried.

• Pigeons!– I only wish I was joking.– Animal rights were still 80 years in the future!

Pigeons??

Photography Types

San Francisco Earthquake - 1906

Making Maps…The Pigeons Retire.

• Mostly the domain of the military.

• Some photographs were taken from a vertical perspective during WW1.

• If you piece them together they look like a map.

• Widely used tool for mapping (accuracy not all that important at this point).

Mapping with Photo’s

Making Measurements.

• Photo mosaics were useful, but they only give you the overview and are not accurate maps.

• In the late 1800’s the development of the parlor stereoscope was a source of entertainment before radio and TV were invented.

Photogrammetry

• The science of taking precise measurements from photographs.

• Took 80 years to make it useful.

• The most important development in map making.

• Very precise measurements can be taken from stereoscopic images.

• Correct distortions, and you have a remote mapping tool (heights, distances, areas).

Photogrammetry

• Removes ground survey as a map making method.– We still do some ground survey, but only of very small

areas.

• Canada at the forefront of this technology.– Vertical aerial photography from Lethbridge starting in

1928.– Large landmass – sovereignty.

• All topographic maps are produced using this technology.

Colour and Remote Sensing

• B&W photographs are still commonly used today.• Colour adds additional information.• Most objects on Earth reflect and absorb different

wavelengths of EMR, producing colour.• If things are different colours, then we can use

colour to tell them apart.– First thought in automated mapping using RS.

• The reflectance/absorption pattern is called a spectral signature.

Spectral Signatures

From Spectral Signatures to Images

• We don’t use all of the spectral information.

• Can’t display the continuous spectrum as an image.– Too much data.– Difficult to interpret.

• Rely on using discrete bands of information.

• Select the relevant areas of greatest change.

Spectral signatures with TM bands

RGB Band Composite